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Kungl. Vetenskapsakademien: The Crafoord Prize in Geosciences 2014

The Royal Swedish Academy of Sciences has decided to award the Crafoord
Prize in Geosciences 2014 to

Peter MolnarUniversity of Colorado Boulder, CO, USA

"for his ground-breaking contribution to the understanding of global
tectonics, in particular the deformation of continents and the structure
and evolution of mountain ranges, as well as the impact of tectonic
processes on ocean-atmosphere circulation and climate."

When continents collide

Why do continents move? How are mountain ranges like the Himalayas and
vast elevated regions like the Tibetan Plateau formed? During the 20th
century, many pieces were laid, one after the other, in the theoretical
puzzle elucidating the dynamics of the Earth's crust and mantle. By
observing and modelling, geoscientists were able to demonstrate not only
that the compositions of oceanic and continental crust were
fundamentally different, but also why these uppermost layers of the
Earth, the key components of the so-called lithospheric plates, moved
and were deformed.

With a background in Geophysics, this year's Crafoord Laureate, Peter
Molnar, has contributed ground-breaking knowledge about the driving
forces behind plate motions and the place of continents in the plate
tectonic model of Earth's evolution. Innovatively combining geological
and geophysical methods of inquiry with satellite measurements and
modelling, the Laureate has also paved the way to a new understanding of
the formation of mountain ranges and their role in global tectonics.

Early in his career, during the latter half of the 1960s, Peter Molnar
pioneered the use of seismology to investigate the relationship between
deep earthquakes and plate motion, demonstrating that the sinking of
oceanic crust into the mantle in subduction zones provides the main
driving force (slab-pull) for moving the plates. Thereafter, Molnar
focused his research on the collision of continents, where deformation
is not concentrated at plate boundaries, but spread over vast areas.
When Molnar and others began to analyse the crust of the Earth,
recognizing its rigidity in upper parts and ductility at lower levels,
and using a continuum mechanics model, crucial discoveries were made.

The Laureate focused his investigations on southern Asia and the
collision between India and Eurasia, a process that began fifty million
years ago and continues today, involving frequent major earthquakes in
the Himalayas and Tibet. Combining interpretations of satellite images
with other geological and geophysical methods of inquiry, including
reconstruction of the plate convergence prior to collision, Molnar and
his colleagues were better able to explain the pattern of deformation in
this continent-continent collision zone.

Their work also demonstrated the fundamental differences between this
and other mountain belts like the Andes, where collision occurs between
oceanic and continental crust and deformation is concentrated along the
plate boundary and above the subduction zone.

By contrast, when continents collide, one is usually thrust beneath the
other and deformation may extend more than a thousand kilometres from
the collision zone, crustal thickness more than doubles, and the
ductility of the lower crust promotes mobility both across and along the
mountain belt. Thus, the Laureate and his colleagues were able to offer
new explanations for the formation of the Himalayas, the elevation of
the Tibetan Plateau and the presence of major faults oriented
approximately perpendicular to the dominant stress field, facilitating
lateral escape of material from the collision zone.

The Crafoord Laureate, still an active researcher, has taken an
interdisciplinary approach not only to the study of processes in the
Earth's crust and mantle, but also to their influence on climate. His
contributions to our knowledge of the formation of mountain ranges and
high plateaux, taken together with evidence for the opening and closing
of seaways between continents has added to our understanding of ocean
current circulation and its influence on regional and global climate.
Peter Molnar's research has also yielded additional knowledge about
earthquake risks, a subject that is highly relevant in the densely
populated areas of the southern Himalayas and also in eastern Tibet.

The Royal Swedish Academy of Sciences, founded in 1739, is an
independent organization whose overall objective is to promote the
sciences and strengthen their influence in society. The Academy takes
special responsibility for the natural sciences and mathematics, but
endeavours to promote the exchange of ideas between various disciplines.